1. Field of the Invention
The present invention relates to the slit exposure optical system used for an electrophotographic copying apparatus or the like, and particularly to a structure for absorbing the impact caused by the stopping of the movable mirror.
2. Description of the Prior Art
As is commonly known, there has been a slit exposure optical system wherein the first movable carriage carrying a light source and the first mirror, and the second movable carriage carrying the second and third mirrors that guide the reflected light from the first mirror to the projection lens are used, and both movable carriages are reciprocated with a ratio of traveling speed of 2:1.
In such slit exposure optical system, a sudden stop of both movable carriages ar their end of travel is needed, and when these movable carriages hit the frame of the apparatus body, the impactive force is transferred to the apparatus body, which is not desirable. In the past, therefore, the stopper cushioned by the spring and the like has been located at the travel end position on the frame of the apparatus body. On such structure, however, it has been impossible to completely eliminate the crashing sound because both movable carriages hit the stopper at considerable high speed and the frame of the apparatus body has been subjected to a considerably impactive force; therefore, not only the frame of the apparatus body vibrates, but also the shock absorbing function of said stopper sometimes becomes ineffective in case of the change in the reciprocating distance of a movable carriage made for the purpose of improvement in the efficiency of continuous copying.